1 /*
   2  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2012, 2018 SAP SE. All rights reserved.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 // no precompiled headers
  27 #include "jvm.h"
  28 #include "asm/assembler.inline.hpp"
  29 #include "classfile/classLoader.hpp"
  30 #include "classfile/systemDictionary.hpp"
  31 #include "classfile/vmSymbols.hpp"
  32 #include "code/codeCache.hpp"
  33 #include "code/icBuffer.hpp"
  34 #include "code/vtableStubs.hpp"
  35 #include "interpreter/interpreter.hpp"
  36 #include "memory/allocation.inline.hpp"
  37 #include "nativeInst_ppc.hpp"
  38 #include "os_share_linux.hpp"
  39 #include "prims/jniFastGetField.hpp"
  40 #include "prims/jvm_misc.hpp"
  41 #include "runtime/arguments.hpp"
  42 #include "runtime/extendedPC.hpp"
  43 #include "runtime/frame.inline.hpp"
  44 #include "runtime/interfaceSupport.hpp"
  45 #include "runtime/java.hpp"
  46 #include "runtime/javaCalls.hpp"
  47 #include "runtime/mutexLocker.hpp"
  48 #include "runtime/osThread.hpp"
  49 #include "runtime/sharedRuntime.hpp"
  50 #include "runtime/stubRoutines.hpp"
  51 #include "runtime/thread.inline.hpp"
  52 #include "runtime/timer.hpp"
  53 #include "utilities/events.hpp"
  54 #include "utilities/vmError.hpp"
  55 
  56 // put OS-includes here
  57 # include <sys/types.h>
  58 # include <sys/mman.h>
  59 # include <pthread.h>
  60 # include <signal.h>
  61 # include <errno.h>
  62 # include <dlfcn.h>
  63 # include <stdlib.h>
  64 # include <stdio.h>
  65 # include <unistd.h>
  66 # include <sys/resource.h>
  67 # include <pthread.h>
  68 # include <sys/stat.h>
  69 # include <sys/time.h>
  70 # include <sys/utsname.h>
  71 # include <sys/socket.h>
  72 # include <sys/wait.h>
  73 # include <pwd.h>
  74 # include <poll.h>
  75 # include <ucontext.h>
  76 
  77 
  78 address os::current_stack_pointer() {
  79   intptr_t* csp;
  80 
  81   // inline assembly `mr regno(csp), R1_SP':
  82   __asm__ __volatile__ ("mr %0, 1":"=r"(csp):);
  83 
  84   return (address) csp;
  85 }
  86 
  87 char* os::non_memory_address_word() {
  88   // Must never look like an address returned by reserve_memory,
  89   // even in its subfields (as defined by the CPU immediate fields,
  90   // if the CPU splits constants across multiple instructions).
  91 
  92   return (char*) -1;
  93 }
  94 
  95 void os::initialize_thread(Thread *thread) { }
  96 
  97 // Frame information (pc, sp, fp) retrieved via ucontext
  98 // always looks like a C-frame according to the frame
  99 // conventions in frame_ppc64.hpp.
 100 address os::Linux::ucontext_get_pc(const ucontext_t * uc) {
 101   // On powerpc64, ucontext_t is not selfcontained but contains
 102   // a pointer to an optional substructure (mcontext_t.regs) containing the volatile
 103   // registers - NIP, among others.
 104   // This substructure may or may not be there depending where uc came from:
 105   // - if uc was handed over as the argument to a sigaction handler, a pointer to the
 106   //   substructure was provided by the kernel when calling the signal handler, and
 107   //   regs->nip can be accessed.
 108   // - if uc was filled by getcontext(), it is undefined - getcontext() does not fill
 109   //   it because the volatile registers are not needed to make setcontext() work.
 110   //   Hopefully it was zero'd out beforehand.
 111   guarantee(uc->uc_mcontext.regs != NULL, "only use ucontext_get_pc in sigaction context");
 112   return (address)uc->uc_mcontext.regs->nip;
 113 }
 114 
 115 // modify PC in ucontext.
 116 // Note: Only use this for an ucontext handed down to a signal handler. See comment
 117 // in ucontext_get_pc.
 118 void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
 119   guarantee(uc->uc_mcontext.regs != NULL, "only use ucontext_set_pc in sigaction context");
 120   uc->uc_mcontext.regs->nip = (unsigned long)pc;
 121 }
 122 
 123 static address ucontext_get_lr(const ucontext_t * uc) {
 124   return (address)uc->uc_mcontext.regs->link;
 125 }
 126 
 127 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t * uc) {
 128   return (intptr_t*)uc->uc_mcontext.regs->gpr[1/*REG_SP*/];
 129 }
 130 
 131 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t * uc) {
 132   return NULL;
 133 }
 134 
 135 ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
 136                     intptr_t** ret_sp, intptr_t** ret_fp) {
 137 
 138   ExtendedPC  epc;
 139   const ucontext_t* uc = (const ucontext_t*)ucVoid;
 140 
 141   if (uc != NULL) {
 142     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 143     if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
 144     if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
 145   } else {
 146     // construct empty ExtendedPC for return value checking
 147     epc = ExtendedPC(NULL);
 148     if (ret_sp) *ret_sp = (intptr_t *)NULL;
 149     if (ret_fp) *ret_fp = (intptr_t *)NULL;
 150   }
 151 
 152   return epc;
 153 }
 154 
 155 frame os::fetch_frame_from_context(const void* ucVoid) {
 156   intptr_t* sp;
 157   intptr_t* fp;
 158   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
 159   return frame(sp, epc.pc());
 160 }
 161 
 162 bool os::Linux::get_frame_at_stack_banging_point(JavaThread* thread, ucontext_t* uc, frame* fr) {
 163   address pc = (address) os::Linux::ucontext_get_pc(uc);
 164   if (Interpreter::contains(pc)) {
 165     // Interpreter performs stack banging after the fixed frame header has
 166     // been generated while the compilers perform it before. To maintain
 167     // semantic consistency between interpreted and compiled frames, the
 168     // method returns the Java sender of the current frame.
 169     *fr = os::fetch_frame_from_context(uc);
 170     if (!fr->is_first_java_frame()) {
 171       assert(fr->safe_for_sender(thread), "Safety check");
 172       *fr = fr->java_sender();
 173     }
 174   } else {
 175     // More complex code with compiled code.
 176     assert(!Interpreter::contains(pc), "Interpreted methods should have been handled above");
 177     CodeBlob* cb = CodeCache::find_blob(pc);
 178     if (cb == NULL || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
 179       // Not sure where the pc points to, fallback to default
 180       // stack overflow handling. In compiled code, we bang before
 181       // the frame is complete.
 182       return false;
 183     } else {
 184       intptr_t* sp = os::Linux::ucontext_get_sp(uc);
 185       address lr = ucontext_get_lr(uc);
 186       *fr = frame(sp, lr);
 187       if (!fr->is_java_frame()) {
 188         assert(fr->safe_for_sender(thread), "Safety check");
 189         assert(!fr->is_first_frame(), "Safety check");
 190         *fr = fr->java_sender();
 191       }
 192     }
 193   }
 194   assert(fr->is_java_frame(), "Safety check");
 195   return true;
 196 }
 197 
 198 frame os::get_sender_for_C_frame(frame* fr) {
 199   if (*fr->sp() == 0) {
 200     // fr is the last C frame
 201     return frame(NULL, NULL);
 202   }
 203   return frame(fr->sender_sp(), fr->sender_pc());
 204 }
 205 
 206 
 207 frame os::current_frame() {
 208   intptr_t* csp = (intptr_t*) *((intptr_t*) os::current_stack_pointer());
 209   // hack.
 210   frame topframe(csp, (address)0x8);
 211   // Return sender of sender of current topframe which hopefully
 212   // both have pc != NULL.
 213   frame tmp = os::get_sender_for_C_frame(&topframe);
 214   return os::get_sender_for_C_frame(&tmp);
 215 }
 216 
 217 // Utility functions
 218 
 219 extern "C" JNIEXPORT int
 220 JVM_handle_linux_signal(int sig,
 221                         siginfo_t* info,
 222                         void* ucVoid,
 223                         int abort_if_unrecognized) {
 224   ucontext_t* uc = (ucontext_t*) ucVoid;
 225 
 226   Thread* t = Thread::current_or_null_safe();
 227 
 228   SignalHandlerMark shm(t);
 229 
 230   // Note: it's not uncommon that JNI code uses signal/sigset to install
 231   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 232   // or have a SIGILL handler when detecting CPU type). When that happens,
 233   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 234   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 235   // that do not require siginfo/ucontext first.
 236 
 237   if (sig == SIGPIPE) {
 238     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 239       return true;
 240     } else {
 241       // Ignoring SIGPIPE - see bugs 4229104
 242       return true;
 243     }
 244   }
 245 
 246   // Make the signal handler transaction-aware by checking the existence of a
 247   // second (transactional) context with MSR TS bits active. If the signal is
 248   // caught during a transaction, then just return to the HTM abort handler.
 249   // Please refer to Linux kernel document powerpc/transactional_memory.txt,
 250   // section "Signals".
 251   if (uc && uc->uc_link) {
 252     ucontext_t* second_uc = uc->uc_link;
 253 
 254     // MSR TS bits are 29 and 30 (Power ISA, v2.07B, Book III-S, pp. 857-858,
 255     // 3.2.1 "Machine State Register"), however note that ISA notation for bit
 256     // numbering is MSB 0, so for normal bit numbering (LSB 0) they come to be
 257     // bits 33 and 34. It's not related to endianness, just a notation matter.
 258     if (second_uc->uc_mcontext.regs->msr & 0x600000000) {
 259       if (TraceTraps) {
 260         tty->print_cr("caught signal in transaction, "
 261                         "ignoring to jump to abort handler");
 262       }
 263       // Return control to the HTM abort handler.
 264       return true;
 265     }
 266   }
 267 
 268   JavaThread* thread = NULL;
 269   VMThread* vmthread = NULL;
 270   if (os::Linux::signal_handlers_are_installed) {
 271     if (t != NULL) {
 272       if(t->is_Java_thread()) {
 273         thread = (JavaThread*)t;
 274       } else if(t->is_VM_thread()) {
 275         vmthread = (VMThread *)t;
 276       }
 277     }
 278   }
 279 
 280   // Moved SafeFetch32 handling outside thread!=NULL conditional block to make
 281   // it work if no associated JavaThread object exists.
 282   if (uc) {
 283     address const pc = os::Linux::ucontext_get_pc(uc);
 284     if (pc && StubRoutines::is_safefetch_fault(pc)) {
 285       os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
 286       return true;
 287     }
 288   }
 289 
 290   // decide if this trap can be handled by a stub
 291   address stub = NULL;
 292   address pc   = NULL;
 293 
 294   //%note os_trap_1
 295   if (info != NULL && uc != NULL && thread != NULL) {
 296     pc = (address) os::Linux::ucontext_get_pc(uc);
 297 
 298     // Handle ALL stack overflow variations here
 299     if (sig == SIGSEGV) {
 300       // Si_addr may not be valid due to a bug in the linux-ppc64 kernel (see
 301       // comment below). Use get_stack_bang_address instead of si_addr.
 302       address addr = ((NativeInstruction*)pc)->get_stack_bang_address(uc);
 303 
 304       // Check if fault address is within thread stack.
 305       if (thread->on_local_stack(addr)) {
 306         // stack overflow
 307         if (thread->in_stack_yellow_reserved_zone(addr)) {
 308           if (thread->thread_state() == _thread_in_Java) {
 309             if (thread->in_stack_reserved_zone(addr)) {
 310               frame fr;
 311               if (os::Linux::get_frame_at_stack_banging_point(thread, uc, &fr)) {
 312                 assert(fr.is_java_frame(), "Must be a Javac frame");
 313                 frame activation =
 314                   SharedRuntime::look_for_reserved_stack_annotated_method(thread, fr);
 315                 if (activation.sp() != NULL) {
 316                   thread->disable_stack_reserved_zone();
 317                   if (activation.is_interpreted_frame()) {
 318                     thread->set_reserved_stack_activation((address)activation.fp());
 319                   } else {
 320                     thread->set_reserved_stack_activation((address)activation.unextended_sp());
 321                   }
 322                   return 1;
 323                 }
 324               }
 325             }
 326             // Throw a stack overflow exception.
 327             // Guard pages will be reenabled while unwinding the stack.
 328             thread->disable_stack_yellow_reserved_zone();
 329             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 330           } else {
 331             // Thread was in the vm or native code. Return and try to finish.
 332             thread->disable_stack_yellow_reserved_zone();
 333             return 1;
 334           }
 335         } else if (thread->in_stack_red_zone(addr)) {
 336           // Fatal red zone violation.  Disable the guard pages and fall through
 337           // to handle_unexpected_exception way down below.
 338           thread->disable_stack_red_zone();
 339           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 340 
 341           // This is a likely cause, but hard to verify. Let's just print
 342           // it as a hint.
 343           tty->print_raw_cr("Please check if any of your loaded .so files has "
 344                             "enabled executable stack (see man page execstack(8))");
 345         } else {
 346           // Accessing stack address below sp may cause SEGV if current
 347           // thread has MAP_GROWSDOWN stack. This should only happen when
 348           // current thread was created by user code with MAP_GROWSDOWN flag
 349           // and then attached to VM. See notes in os_linux.cpp.
 350           if (thread->osthread()->expanding_stack() == 0) {
 351              thread->osthread()->set_expanding_stack();
 352              if (os::Linux::manually_expand_stack(thread, addr)) {
 353                thread->osthread()->clear_expanding_stack();
 354                return 1;
 355              }
 356              thread->osthread()->clear_expanding_stack();
 357           } else {
 358              fatal("recursive segv. expanding stack.");
 359           }
 360         }
 361       }
 362     }
 363 
 364     if (thread->thread_state() == _thread_in_Java) {
 365       // Java thread running in Java code => find exception handler if any
 366       // a fault inside compiled code, the interpreter, or a stub
 367 
 368       // A VM-related SIGILL may only occur if we are not in the zero page.
 369       // On AIX, we get a SIGILL if we jump to 0x0 or to somewhere else
 370       // in the zero page, because it is filled with 0x0. We ignore
 371       // explicit SIGILLs in the zero page.
 372       if (sig == SIGILL && (pc < (address) 0x200)) {
 373         if (TraceTraps) {
 374           tty->print_raw_cr("SIGILL happened inside zero page.");
 375         }
 376         goto report_and_die;
 377       }
 378 
 379       CodeBlob *cb = NULL;
 380       // Handle signal from NativeJump::patch_verified_entry().
 381       if (( TrapBasedNotEntrantChecks && sig == SIGTRAP && nativeInstruction_at(pc)->is_sigtrap_zombie_not_entrant()) ||
 382           (!TrapBasedNotEntrantChecks && sig == SIGILL  && nativeInstruction_at(pc)->is_sigill_zombie_not_entrant())) {
 383         if (TraceTraps) {
 384           tty->print_cr("trap: zombie_not_entrant (%s)", (sig == SIGTRAP) ? "SIGTRAP" : "SIGILL");
 385         }
 386         stub = SharedRuntime::get_handle_wrong_method_stub();
 387       }
 388 
 389       else if (sig == SIGSEGV &&
 390                // A linux-ppc64 kernel before 2.6.6 doesn't set si_addr on some segfaults
 391                // in 64bit mode (cf. http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.6),
 392                // especially when we try to read from the safepoint polling page. So the check
 393                //   (address)info->si_addr == os::get_standard_polling_page()
 394                // doesn't work for us. We use:
 395                ((NativeInstruction*)pc)->is_safepoint_poll() &&
 396                CodeCache::contains((void*) pc) &&
 397                ((cb = CodeCache::find_blob(pc)) != NULL) &&
 398                cb->is_compiled()) {
 399         if (TraceTraps) {
 400           tty->print_cr("trap: safepoint_poll at " INTPTR_FORMAT " (SIGSEGV)", p2i(pc));
 401         }
 402         stub = SharedRuntime::get_poll_stub(pc);
 403       }
 404 
 405       // SIGTRAP-based ic miss check in compiled code.
 406       else if (sig == SIGTRAP && TrapBasedICMissChecks &&
 407                nativeInstruction_at(pc)->is_sigtrap_ic_miss_check()) {
 408         if (TraceTraps) {
 409           tty->print_cr("trap: ic_miss_check at " INTPTR_FORMAT " (SIGTRAP)", p2i(pc));
 410         }
 411         stub = SharedRuntime::get_ic_miss_stub();
 412       }
 413 
 414       // SIGTRAP-based implicit null check in compiled code.
 415       else if (sig == SIGTRAP && TrapBasedNullChecks &&
 416                nativeInstruction_at(pc)->is_sigtrap_null_check()) {
 417         if (TraceTraps) {
 418           tty->print_cr("trap: null_check at " INTPTR_FORMAT " (SIGTRAP)", p2i(pc));
 419         }
 420         stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 421       }
 422 
 423       // SIGSEGV-based implicit null check in compiled code.
 424       else if (sig == SIGSEGV && ImplicitNullChecks &&
 425                CodeCache::contains((void*) pc) &&
 426                !MacroAssembler::needs_explicit_null_check((intptr_t) info->si_addr)) {
 427         if (TraceTraps) {
 428           tty->print_cr("trap: null_check at " INTPTR_FORMAT " (SIGSEGV)", p2i(pc));
 429         }
 430         stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 431       }
 432 
 433 #ifdef COMPILER2
 434       // SIGTRAP-based implicit range check in compiled code.
 435       else if (sig == SIGTRAP && TrapBasedRangeChecks &&
 436                nativeInstruction_at(pc)->is_sigtrap_range_check()) {
 437         if (TraceTraps) {
 438           tty->print_cr("trap: range_check at " INTPTR_FORMAT " (SIGTRAP)", p2i(pc));
 439         }
 440         stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 441       }
 442 #endif
 443       else if (sig == SIGBUS) {
 444         // BugId 4454115: A read from a MappedByteBuffer can fault here if the
 445         // underlying file has been truncated. Do not crash the VM in such a case.
 446         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 447         CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
 448         if (nm != NULL && nm->has_unsafe_access()) {
 449           address next_pc = pc + 4;
 450           next_pc = SharedRuntime::handle_unsafe_access(thread, next_pc);
 451           os::Linux::ucontext_set_pc(uc, next_pc);
 452           return true;
 453         }
 454       }
 455     }
 456 
 457     else { // thread->thread_state() != _thread_in_Java
 458       if (sig == SIGILL && VM_Version::is_determine_features_test_running()) {
 459         // SIGILL must be caused by VM_Version::determine_features().
 460         *(int *)pc = 0; // patch instruction to 0 to indicate that it causes a SIGILL,
 461                         // flushing of icache is not necessary.
 462         stub = pc + 4;  // continue with next instruction.
 463       }
 464       else if (thread->thread_state() == _thread_in_vm &&
 465                sig == SIGBUS && thread->doing_unsafe_access()) {
 466         address next_pc = pc + 4;
 467         next_pc = SharedRuntime::handle_unsafe_access(thread, next_pc);
 468         os::Linux::ucontext_set_pc(uc, pc + 4);
 469         return true;
 470       }
 471     }
 472 
 473     // Check to see if we caught the safepoint code in the
 474     // process of write protecting the memory serialization page.
 475     // It write enables the page immediately after protecting it
 476     // so we can just return to retry the write.
 477     if ((sig == SIGSEGV) &&
 478         // Si_addr may not be valid due to a bug in the linux-ppc64 kernel (see comment above).
 479         // Use is_memory_serialization instead of si_addr.
 480         ((NativeInstruction*)pc)->is_memory_serialization(thread, ucVoid)) {
 481       // Synchronization problem in the pseudo memory barrier code (bug id 6546278)
 482       // Block current thread until the memory serialize page permission restored.
 483       os::block_on_serialize_page_trap();
 484       return true;
 485     }
 486   }
 487 
 488   if (stub != NULL) {
 489     // Save all thread context in case we need to restore it.
 490     if (thread != NULL) thread->set_saved_exception_pc(pc);
 491     os::Linux::ucontext_set_pc(uc, stub);
 492     return true;
 493   }
 494 
 495   // signal-chaining
 496   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 497     return true;
 498   }
 499 
 500   if (!abort_if_unrecognized) {
 501     // caller wants another chance, so give it to him
 502     return false;
 503   }
 504 
 505   if (pc == NULL && uc != NULL) {
 506     pc = os::Linux::ucontext_get_pc(uc);
 507   }
 508 
 509 report_and_die:
 510   // unmask current signal
 511   sigset_t newset;
 512   sigemptyset(&newset);
 513   sigaddset(&newset, sig);
 514   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 515 
 516   VMError::report_and_die(t, sig, pc, info, ucVoid);
 517 
 518   ShouldNotReachHere();
 519   return false;
 520 }
 521 
 522 void os::Linux::init_thread_fpu_state(void) {
 523   // Disable FP exceptions.
 524   __asm__ __volatile__ ("mtfsfi 6,0");
 525 }
 526 
 527 int os::Linux::get_fpu_control_word(void) {
 528   // x86 has problems with FPU precision after pthread_cond_timedwait().
 529   // nothing to do on ppc64.
 530   return 0;
 531 }
 532 
 533 void os::Linux::set_fpu_control_word(int fpu_control) {
 534   // x86 has problems with FPU precision after pthread_cond_timedwait().
 535   // nothing to do on ppc64.
 536 }
 537 
 538 ////////////////////////////////////////////////////////////////////////////////
 539 // thread stack
 540 
 541 // Minimum usable stack sizes required to get to user code. Space for
 542 // HotSpot guard pages is added later.
 543 size_t os::Posix::_compiler_thread_min_stack_allowed = 64 * K;
 544 size_t os::Posix::_java_thread_min_stack_allowed = 64 * K;
 545 size_t os::Posix::_vm_internal_thread_min_stack_allowed = 64 * K;
 546 
 547 // Return default stack size for thr_type.
 548 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 549   // Default stack size (compiler thread needs larger stack).
 550   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1024 * K);
 551   return s;
 552 }
 553 
 554 /////////////////////////////////////////////////////////////////////////////
 555 // helper functions for fatal error handler
 556 
 557 void os::print_context(outputStream *st, const void *context) {
 558   if (context == NULL) return;
 559 
 560   const ucontext_t* uc = (const ucontext_t*)context;
 561 
 562   st->print_cr("Registers:");
 563   st->print("pc =" INTPTR_FORMAT "  ", uc->uc_mcontext.regs->nip);
 564   st->print("lr =" INTPTR_FORMAT "  ", uc->uc_mcontext.regs->link);
 565   st->print("ctr=" INTPTR_FORMAT "  ", uc->uc_mcontext.regs->ctr);
 566   st->cr();
 567   for (int i = 0; i < 32; i++) {
 568     st->print("r%-2d=" INTPTR_FORMAT "  ", i, uc->uc_mcontext.regs->gpr[i]);
 569     if (i % 3 == 2) st->cr();
 570   }
 571   st->cr();
 572   st->cr();
 573 
 574   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 575   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
 576   print_hex_dump(st, (address)sp, (address)(sp + 128), sizeof(intptr_t));
 577   st->cr();
 578 
 579   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 580   // point to garbage if entry point in an nmethod is corrupted. Leave
 581   // this at the end, and hope for the best.
 582   address pc = os::Linux::ucontext_get_pc(uc);
 583   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", p2i(pc));
 584   print_hex_dump(st, pc - 64, pc + 64, /*instrsize=*/4);
 585   st->cr();
 586 }
 587 
 588 void os::print_register_info(outputStream *st, const void *context) {
 589   if (context == NULL) return;
 590 
 591   const ucontext_t *uc = (const ucontext_t*)context;
 592 
 593   st->print_cr("Register to memory mapping:");
 594   st->cr();
 595 
 596   // this is only for the "general purpose" registers
 597   for (int i = 0; i < 32; i++) {
 598     st->print("r%-2d=", i);
 599     print_location(st, uc->uc_mcontext.regs->gpr[i]);
 600   }
 601   st->cr();
 602 }
 603 
 604 extern "C" {
 605   int SpinPause() {
 606     return 0;
 607   }
 608 }
 609 
 610 #ifndef PRODUCT
 611 void os::verify_stack_alignment() {
 612   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
 613 }
 614 #endif
 615 
 616 int os::extra_bang_size_in_bytes() {
 617   // PPC does not require the additional stack bang.
 618   return 0;
 619 }